Best app for charting temp

Can anyone recommend a good app for me to chart my temperature on? AF has just come back after 16months of bfeeding, and I've gone from a 40 day cycle Pre-pregnancy, to an 18 day cycle!!!!! No idea even if I'm ovulating. Tried temperature charting before and after a year of no luck got a BFP.... so hoping it will work the same magic again.

Any recommendations of an app that is quick, simple, and gives me a pretty graph to look at?